It's true that your gut biome is awesome, complicated, poorly understood and crucial to your body's normal functioning.
But "probiotic" supplements are a largely unregulated category of goods, filled with random, mislabeled microorganisms, making health claims based on extremely thin and shaky science.
The thin science isn't the supplements makers' fault, entirely. The FDA's protocol for testing the health effects of drugs isn't well-suited to micro-organisms, and is slow and difficult to perform.
But that doesn't excuse the mislabelling of the pills themselves. What's more, without any solid science on ingesting microorganisms, you're basically self-medicating at random. Some researchers believe that heavy dosing of probiotic supplements could lead to selectively breeding hardier versions of harmful bacteria, reducing or exhausting whatever health benefits probiotics could deliver before they're even formalized and optimized.
So should a healthy person take a daily probiotic supplement to "maintain digestive balance" or "support immune health," as the packaging claims?
The half-dozen doctors and gastroenterologists interviewed for this article said no, some more vehemently than others.
"Absolutely no," said Fasano.
To be sure, most bacterial strains labeled "probiotic" are safe. Humans have been ingesting such bacteria in food for centuries and in supplements for decades, with few reported side effects.
But doctors are wary because the health benefits have not been proved, and because it's hard to know exactly what's in commercial products. At least seven studies have found discrepancies between what's on the label and what's in the product, especially in products containing multiple bacterial strains. A 2015 analysis of 16 probiotic products, for example, found that only one of 16 exactly matched the bacterial species claims on the label in every sample tested.
Probiotics come with bold health claims, but the science is shaky [Megan Scudellari/Stat News]
(Image: Scanning electron micrograph of en:Clostridium difficile bacteria, CDC, Lois S. Wiggs)